Re: ensure a VPATH build

[Keith MARSHALL]

Ralf Wildenhues wrote, quoting me:
>> I fixed it by moving the backticked expression outside of the
>> outer quotes.
>
> Yes.  Note that some more quotes are unnecessary here; this
>   MATCH="$MATCH"`echo --$OPT | $GREP "^$OPTNAME"`
>
> can safely be rewritten like this:
>   MATCH=$MATCH`echo --$OPT | $GREP "^$OPTNAME"`
>
> simply because the shell does not do word-splitting on the right
> hand sides of assignments.

Agreed, the double quotes here are redundant;  but they are also
harmless, and I happen to prefer the quoted form, in this case.

> By the way, what about the other mentioned issue in above thread?
> The
>   ./pdfroff: 561: Syntax error: "}" unexpected (expecting "fi")

This has since been fixed too.

> I do not have access to a system exposing this issue, but a wild
> guess would be that the shell in question has trouble with this
> construct:
>   "${foo+"set"}"

Not such a wild guess; the problem was related to this, in a more
complex construct:

  CS_FILTER="$STREAM $SED -n '/${DOT}${CS_MACRO-"CS"}/,\
      /${DOT}${CE_MACRO-"CE"}/p'"

Moving the default substitutions for CS_MACRO and CE_MACRO out of
the expression, initialising them on a preceeding line on their own,
was sufficient to eliminate the problem.

Curiously, these similar constructs:

  IFS="${PATH_SEPARATOR-":"}" prog=':'

and

  test "${SHOW_PROGRESS+"set"}" = "set" && SAY=echo

didn't result in a similar problem, and I overlooked them when I
applied the original correction.  There haven't been any further bug
reports in the eight months since, but it may still be wise to apply
your patch proactively.  Thanks.

> BTW, in the patch [snipped], the
>   >> $REFFILE
> looks problematic to me.  What is it supposed to do?

I've never encountered a shell which has trouble with this idiom
for touching a file, leaving it unmodified if it already exists, or
creating it (empty) if it doesn't;  (even MS-DOS' command.com can
handle it, in the form `>> %REFFILE%', in its .bat language).  I
won't change this, unless you can provide evidence of a specific
arena in which it fails.

Regards,
Keith.